1. Field of the Invention
The invention relates to an artificial sphincter for maintaining continence in those patients unable to control or stop inadvertent urinary flow. More particularly, the invention relates to a hydraulic sphincter (MAHS) which: automatically causes sphincter pressure to increase or decrease with bladder pressure and/or abdominal pressure; is manually actuated by the patient when he or she desires to urinate; and, allows sphincter fluid pressure to be measured and adjusted after implantation without necessitating a surgical procedure.
2. Description of the Prior Art
Urinary incontinence is a ubiquitous disorder which represents more than a personal inconvenience and social problem. For many, particularly those individuals suffering spinal injury, incontinence can cause life threatening complications. In the United States alone, it is estimated that 100,000 persons of all ages, many of them young veterans, have sustained spinal cord injuries rendering them incontinent. Pyelonephritis, a kidney infection produced by bacterial spread from the lower urinary tract, has been the leading cause of death among paralyzed World War II and Korean war veterans. Neurologic dysfunction of the urinary sphincter can also occur because of multiple sclerosis, stroke, cerebrovascular disease, Parkinson disease and diabetes. Approximately 20% of the population over 65 suffer from incontinence. Women suffer "stress incontinence" largely the result of changes in bladder geometry following child birth. Many men experience incontinence after prostate surgery. Finally, incontinence can result from meningomyelocoele, amyotrophic lateral sclerosis, spinal cord or brain tumor, head injury, herniated disc, syringomyelia and tabes dorsalis.
Various attempts have been made to artificially produce urinary continence. Early attempts to prevent male incontinence involved externally clamping the penis; but, pressure sufficient to stop urinary flow tends also to compromise circulation, causing pain, skin alteration and thrombosis. An analogous application for women, compressing the urethra between the vaginal wall and the pubic bone, shares these disadvantages.
Several implantable artificial sphincters have, more recently, been disclosed in the prior art. U.S. Pat. No. 4,256,093 issued to Curtis Helms et al teaches the use of a fluid filled urethra collar which is contracted by manually squeezing a bulb implanted in the scrotum. In an article entitled "Implantation of an Artificial Sphincter for Urinary Incontinence" by F. B. Scott et al, in Contemporary Surgery, Vol. 18, Feb. 1981, results with such prior art artificial sphincters are reported. The article focuses on typical prior art devices which require a bulbous pump to be implanted in the scrotum of the male or in the labium of the female. In order to initiate urine flow the patient must compress the bulbous pump. The prior art devices are psychologically and cosmetically undesirable because of a general aversion most patients have to touching implants in such sensitive portions of the bodies as the scrotum and labium.
U.S. Pat. No. 3,815,576 issued to Donald R. Balaban teaches the use of a fluid filled flexible container implanted in the patient which is squeezed manually to actuate a piston-cylinder in a U-shaped clamp. Similarly, U.S. Pat. No. 4,056,095 issued to Pierre Rey et al and U.S. Pat. No. 4,0178,915 issued to Gerhard Szinicz et al teach the use of a fluid filled artificial sphincter which is actuated by pressing on the subcutaneously implanted membrane. These references share the disadvantage of having no control over the pressure exerted by the artificial sphincter on the urethra once the apparatus is implanted.
During the course of a research study (G. Timm et al, "Experimental Evaluation of an Implantable Externally Controllable Urinary Sphincter", Investigative Urology 11:326-330, 1974) it was found that artificial sphincter cuff pressure of 40 cm of H.sub.2 O and above produce necrosis (tissue death) of the urethra. As a result, the prior art devices generally operate at a cuff pressure below 40 cm of H.sub.2 O. However, the normal bladder (and also the hypertrophic bladder), can produce high pressure transients, which results in drippling incontinence for patients with these devices. U.S. Pat. No. 3,744,063 issued to McWhorter et al teaches controlling the flow of a fluid into the sphincter so that pressure applied to the urethra is graduated and controlled. However, variable pressure is controlled manually by applying digital pressure to an implanted pump chamber. Presumably, the patient increases the sphincter pressure after drippling incontinence has occurred and been detected. The patient would not be able to respond to rapid changes in bladder pressure caused by bladder spasms, voluntarily or involuntary tensing of the diaphragm or abdominal wall, or increased intra-abdominal pressure due to walking, sitting, coughing or laughing.
The August 1981 issue of Urology Times contains an article reporting on an address by Dr. T. R. Malloy of the Pennsylvania Hospital in Philadelphia. Dr. Malloy has discovered that to reduce necrosis of the urethra it is necessary to have the artificial sphincter unfilled upon initial implant. It was found that urethra tissue swells immediately after surgery. If the artificial sphincter is filled it will exert an excessive pressure on the swollen urethra resulting in tissue necrosis. Dr. Malloy recommends allowing the swelling to decrease, followed by a second operation at a later time, merely to fill the sphincter chamber with fluid. The prior art artificial sphincters have no way of adding or replacing fluid in the artificial sphincter without surgery. Therefore, successful implantation of prior art devices requires two separate surgical operations.